How Radiation Damages Cancer Cells

Why exactly are cancerous cells more damaged by radiation than normal cells?

Cancerous cells are more damaged by radiation compared to normal cells due to several factors:

1. Increased Metabolic Activity: Cancer cells are characterized by rapid and uncontrolled growth, which requires a high amount of energy. This results in increased metabolic activity compared to normal cells. Radiation damages DNA by causing breaks or cross-links, and cancer cells, with their higher metabolic rate, have a greater chance of sustaining such damage.

2. Impaired DNA Repair Mechanisms: Normal cells have well-functioning DNA repair systems that help fix DNA damage promptly. However, in cancer cells, these repair systems are often defective or impaired. Radiation-induced damage overwhelms the repair capacity of cancer cells, leading to higher levels of unrepaired DNA damage, ultimately resulting in a higher chance of cell death or mutations.

3. Reduced Cell Cycle Control: Cancer cells often have altered cell cycle control, leading to uncontrolled cell division and replication. Radiation primarily damages DNA during the cell replication process, when the DNA is being copied. Cancer cells may have a compromised cell cycle control, leading to a higher likelihood of radiation-induced DNA damage during replication.

4. Altered Cellular Signaling Pathways: Cancer cells exhibit abnormal signaling pathways that govern their survival, growth, and response to stress. Radiation interferes with these pathways, making it more challenging for cancer cells to repair the DNA damage and recover from the radiation insult.

5. Enhanced Sensitivity to Reactive Oxygen Species (ROS): Radiation can generate reactive oxygen species (ROS), highly reactive molecules that can damage DNA. Cancer cells often have elevated levels of ROS due to their increased mitochondrial activity, defective antioxidant systems, or impaired activation of DNA repair enzymes. This higher baseline ROS level makes cancer cells more susceptible to additional ROS generated by radiation and increases the cumulative DNA damage.

6. Genetic Instability: Cancer cells frequently exhibit genomic instability and have acquired various mutations during their development. This genetic instability makes cancer cells more susceptible to radiation-induced DNA damage. Additionally, cancer cells may have alterations in proteins involved in DNA damage sensing or repair, making them prone to accumulating further damage after exposure to radiation.

It is important to note that while radiation can be selectively damaging to cancer cells, it also affects surrounding normal tissues. However, the strategies used in radiation therapy aim to deliver the highest possible dose to cancer cells while minimizing the impact on healthy tissues.

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